Froth flotation of sylvinite ore



Patented Sept. 15, 1953 UNITED STATES PATENT OFFICE morn FLOTATION F srLvIN r oaE Arthur J. Weinig, Golden, 0010., assignor to Potash Company of America, Denver, 0010., a

corporation of Colorado No Drawing. Application April3, 1948,

' Serial No. 18,847

17 Claims. (Cl. 209.16,6)

My invention relates generally to improvements in the art of frothflotation and is directed particularly to reagents employed in froth flotation for effecting a separation of sodium chloride and other impurities, such as, clay, polyhalite, anhydrite or the like from potassium salts, such as potassium chloride.

As taught by the prior art, ores containing potassium salts can be processed by froth flotation utilizing a brine saturated with respect to the soluble components of the ore as a liquid media to form an ore pulp. Variouscollector reagents, such as fatty acids, salt water soaps or naphthenic acids are utilized in these processes, but are most effective in'the absence of slime and in the presence of a soluble 'lead'salt in the brine. Finely ground ores do'notrespondwell to these reagents in the conyentional process, and the brines are h hly q r q reio t meta eq ipment which they contact ,duringftl e processing cycle.

A primary object of my invention is to overcome these and other defects in the priorart through the provision of a'novel collector reagent for such ores which is effective on finely ground ores and even in the absence of lead and which permits the incorporation of corrosion-inhibiting compounds without detrimental reaction.

Further objects include the provision of reagents and process for utilizing the reagents which may be used in conjunction with other collector reagents and therebyreduce the minimum quantities of the other reagents.

Other objects will become apparent to those skilled in the art from the followingdetailed description and specific examples of my inyention.

In brief, I have found that soluble compounds incorporating the 2,4'-,dichlorophenoxyacetic radical, such as the sodium salt of 2, 1,-d ichloro.- phenoxyacetic acid are highly satisfactory .collector reagents for the flotationof sodium chlo ride or halite, clays and gangue mineralsfrom potassium salts, such aspotassium chloridefor sylvite. Furthermore, the".eifi oiehcy of this re.-

agent as a collector increases asthe fineness ofv grind of the ore is increasedwithin reasonable limits, its efiiciencybeing .sufli ciently great when the ore is ground'to .approx irnately l0 0 mesh to permit its economic use witho'utth'e addition of soluble lead salts to the brine.

Since lead need not be employed when using this rea ent, I ma add to the brine. solu l sa ts containing a bi-chromateor permanganate radie cal to inhibit the corrosive action .of the brine on metal equipment. Theefiect of treating po- 2 tassium salts by my process is somewhat unusual in that, when. the potassium salts are used as fertilizer the beneficial stimulating effect on the plants appears .to be substantially increased.

As a matter of convenience, the soluble compounds of 2A1dichlorophenoxyacetic acid, such as the alkali metal salts ,or esters, will be referred to in the following detailed examples by the abbreviation 2,4-13. Actually 2,4-D itself is sufficiently soluble in the brine to serve as a collector reagent, but the difficulty experienced in dissolving this reagent is avoided by utilizing the sodium salt, which is fully as efficient. However, all soluble compounds yielding the ZA-dichlorophenoxyacetic ion in solution are satisfactory.

As a specific example of the utilization of 2,4-D as a collector, I may employ the reagent as a substitute, either in .whole or in part, for the collector reagent conventionally employed in a froth flotation process for the benefication of sylvinite ores, particularly of the type found in the area near Carlsbad, New Mexico. In general, this process utilizes, as acarrier for the ground ore, a brine saturated with respect to the soluble components of the .ore, this'brine being circulated continuously in a closed circuit and added to the ore either before ,or after grinding, I may grind the ore, as in a ball mill, to approximately 100 mesh, and after the addition of the brine to the ore, I add 2,4-D as a collector reagent, usually with a small amount .of starch to control the character of the froth. The amount of 2,4-D to be added is of course dependent, to some extent, upon the character of the ore. In most instances, however, 0.80 pound per ton of ore will be required until such time as the brine in the circuit approaches saturation with respect to the 2,l- D,'at which time the quantity may be reduced to as little as 0.10 pound per ton of ore. The addition of a soluble salt of lead in this, as in other similar cases, permits the use of smaller quantities of collector reagent, somewhat larger amounts being required if the lead ion is not present in the brine.

The reagents are preferably mixed thoroughly with the pulp, which is then conducted to a series of froth flotation cells-wherein the pulp is aerated to form a froth. The sodium chloride or halite, and clays and gangue minerals are collected by the 2,4-D in the froth which rises to the surface process as a purified non-floated residue from the froth flotation cells, after which it may be further treated, as by filtration and drying, for subsequent use.

It should not be understood that grinding to approximately 100 mesh is essential in instances where 2,4-D is to be employed as a collector reagent, since more conventional grinds, such as about 35 mesh, may be employed efi'iciently provided small quantities of a soluble lead salt, such as 0.51 gram per liter of brine is added to the circuit. The presence of the lead ion, as previously mentioned, permits a marked reduction in the minimum amount of collector reagents required to obtain a satisfactorily high grade of concentrate, and its use, therefore, is often highly desirable from a practical standpoint. The presence of a lead ion in the brine, however, renders ineffective corrosion inhibiting reagents such as soluble bi-chromate or permanganate salts. In instances where lead salts are not utilized, I prefer to add 1-2 grams per liter of brine of a soluble bi-chromate or permanganate salt, such as sodium bi-chromate or potassium permanganate. These compounds greatly reduce the rate of corrosion and thereby effect a very substantial over-all saving in the process, the effect of these salts on the action of the collector reagent being negligible.

It is also feasible to employ 2,4-D as a collector reagent in conjunction with other conventional collector reagents, such as the fatty acids and salts thereof, the 2,4-D reducing proportionately the quantity of other collector reagents required. No adverse effects have been noted by the addition of other common additive reagents, such as starch, which may be used in conventional quantities, as for example, 0.25 pound of starch per ton of ore processed. Cresylic acid may also be used as a frother.

The precise method of utilizing my invention will be more apparent from the following test data, which is obtained from a series of tests run on sylvinite ore, containing about 35% KCl, obtained from the Carlsbad, New Mexico area. This ore, except when noted to the contrary, was crushed to pass through a 35 mesh screen and was processed in a brine formed by saturating Carlsbad water with the soluble components of the ore. The sodium salt of 2,4-dichlorophenoxyacetic acid was dissolved in water to form a 2 per cent solution which had a pH value of about 10.5, this value being obtained by neutralization of the solution with sodium hydroxide.

Test No. 1

To determine the consumption of 2,4-D a circulating brine containing 2 grams of soluble lead per liter was used, the brine being used over again in each successive experiment. Starch at a rate of 0.5 pound per ton of ore was added to obtain a For comparison with Test No. 1, a similar series of experiments were conducted, using a 1 per cent soap solution formed from v 90 per cent caprylic acid. Starch, at a rate of 0.25 pound per '4 ton of ore, and cresylic acid, at a rate of 0.32 pound per ton of ore, were added to the brine. The results of the first, fourth and fifth experiments were as follows:

Caprylic Conc. Tails P Soap Percent Percent erceut Lb./Ion KOL KOL Recwery No. 1, Original Brine 0.20 95.2 4. 5 78. 0 No. 4, Brine from 3 Precedceding Tests 0.08 98.0 4. 4 94. 1 No. 5, Brine from No. 4 0.06 83. 4 4. 3 86. 6

Test No. 3

A series of experiments were conducted to determine the effect of lead upon the quantity of 2,4-D required to obtain a satisfactorily high grade of concentrate. These results were as fol- From the foregoing test, it may be seen that approximately 1 pounds of 2,4-D per ton of ore was required to obtain a satisfactory concentrate when 0.5 gram of lead per liter of brine was present. If, however, the concentration of lead in the brine is doubled, only 0.60 pound of 2,4-D per ton of ore was necessary.

Test No. 4

To determine the effect of finegrinding of the ore in a process using 2,4-D as a collector reagent, the same ore as used in the preceding tests was ground and processed as indicated below:

Cone Tails 2 4-D Percent Ore Size Mesh Percent Percent Lb./Ton K01 K01 Recovery This test proves that the efficiency of 2,4-D as a collector reagent increases as the fineness of grind of the ore increases and that remarkably high grade concentrate can be obtained even in the absence of lead when 2,4-D is used as a collector reagent.

Test N 0. 5

To determine the suitability of ore processed with 2,4-D to subsequent processing procedures, the treatment described in Weinig 2,211,396 was employed.

Sylvinite ore containing 39.1 potassium chloride was ground to -48 mesh and mixed with six parts of saturated brine. 1.5 grams sodium bichromate per liter of brine and 2 pounds 2,4-D per ton of ore were added. By froth flotation the following yields were obtained:

Percent Percent W KC] N aCl plus gangue froth 70. 5 15. 4 K01 flotation tailings 29. 5 95. 8

The sodium chloride plus gangue froth was Percent Percent Wt. K01

Final NaOl and gangue 60.3 0. Final KO] 39. 7 9s. 4

No lead was used in this test, but a satisfactory concentrate was obtained using 2 pounds 2,4-D per ton of ore when ground to -48 mesh.

The foregoing data constitutes only a portion of the data obtained from an extensive series of tests. The remaining data may be summarized by stating that quantities in excess of three pounds of 2,4-D per ton of ore are usually not required and that 2,4-D is not sensitive to the addition of other reagents, provided that detrimental chemical reaction does not occur between 2-,4-1) and the other reagents.

Potassium chloride treated in accordance with the teachings of this invention was employed as a fertilizer for various plants in a test plot for comparison with potassium chloride processed by the conventional process known to the art. The seeds in the plot fertilized with the potassium chloride processed according to my invention, sprouted three days earlier than the seeds in the comparative plots and were of a very markedly more robust nature. The reason for this increase in efliciency of the potassium chloride when used as a fertilizer is not clearly understood, since it would be expected that a majority, at least, of the 2,4-D lost from the circuit in processing would pass from the system with the halite in the froth.

t is possible, however, that small quantities of 2,4-D are adsorbed on the surface of the potassium chloride crystals and that conventional washing procedures are not effective to remove this minute deposit.

It will be understood that certain changes and modifications may be made in my invention without departing from the spirit and scope thereof as defined in the appended claims.

I claim:

1. In a process for the separation of sylvite and halite by froth flotation from a saturated pulp of the ore, the improvement which comprises adding to the pulp a brine soluble salt of 2,4-dichlorophenoxyacetic acid.

2. In a process for separating sylvite and halite by froth flotation from a saturated pulp of the ore, the improvement which comprises adding to the pulp the sodium salt of 2,4-dichlorophenoxyacetic acid.

3. The process for separating sylvite and halite which comprises forming a pulp of ground ore in a saturated brine solution of the ore, the largest particles of ore in the pulp being on the order of 100 mesh, adding to the brine a brine soluble salt of 2, i-dichlorophenoxyacetic acid and subjecting the pulp to froth flotation treatment.

4. The process of separating sylvite from halite which comprises forming a pulp of ground ore in a saturated brine solution of the ore, the largest particle of ore in the pulp being on the order of 48 mesh, adding a brine soluble salt of 2,4-dichlorophenoxyacetic acid and a corrosion inhibilead salt and a collector reagent comprising .a

6. tor selected from a ,cla1ss consisting of soluble bichromate and permanganate salts .to the pulp and subjecting the pulp to'frothflotation treatment.

5. The process for treatingsylvinite ore which includes the steps of forming .a pulp of the ore in a brine solution saturated with respect to the ore components, adding a brine soluble lead salt and a collector reagent comprising a brine soluble salt of 2,4-dichloropherioxyacetic acid to the pulp and subjecting the pulp-to froth flotation.

6. 'The process for treating sylvinite ore which includes the steps of forming a pulp of the ore in a brine solution saturated with respect to the ore components, adding starch, a brine soluble brine soluble. salt .of. 2,4.-dichlorophenoxyacetic acid to the pulp and subjecting the pulp to froth flotation.

7. A process for benefication of an ore containing halite and sylvite, which includes the steps of forming a pulp of the ore in an aqueous brine saturated with respect to the water-soluble components and containing 2,4-dichlorophenoxyacetic ions, and thereafter subjecting the pulp to froth flotation.

8. The process of claim 7 wherein not less than 0.10 pound per ton of ore and not more than 3.0 pounds per ton of ore of the sodium salt of 2,4-di-- chlorophenoxyacetic acid is added to the pulp.

9. The process of claim '7 wherein a fatty acid compound and a soluble salt of 2,4-dichlorophe-- noxyacetic acid are added to the pulp.

10. A process as defined in claim '7 in which the ore contains a minor quantity of clay.

11. A process as defined in claim 7 in which the: ore contains some polyhalite.

12. A process as defined in claim '7 in which the ore contains some anhydrite.

13. The method of separating sylvite from halite by froth flotation in the absence of a soluble lead salt which comprises the steps of grinding the ore to approximately mesh, forming a pulp in a saturated brine solution of the ore, adding to said pulp sodium bichromate and sodium salt of 2,4-dichlorophenoxyacetic acid to the pulp and floatin halite from sylvite by froth flotation.

14. In the process for separating sylvite from halite by froth flotation wherein a pulp of the ore is formed by suspending ground particles of the ore in a brine solution saturated with respect to the soluble ore components, the improvement which comprises adding to the pulp a brinesoluble collector reagent yielding 2,4-dichlorophenoxyacetic ions and a soluble bichromate or permanganate salt in the absence of lead.

15. The method for benefication of an ore containing sylvite and halite, which includes the steps of forming a pulp of an ore ground to an average particle size not smaller than about 100 mesh, forming a pulp of the ore in an aqueous brine saturated with respect to the soluble ore components and substantially free of lead ions, dissolving in the pulp not less than 0.80 pound per ton of ore, nor more than 3 pounds per ton of ore of a brine-soluble collector reagent, liberating 2,4-dichlorophenoxyacetic ions in solution, and thereafter concentrating halite in the froth by subjecting the pulp to froth flotation.

16. The process for benefication of an ore containing halite and sylvite, which includes the steps of forming a pulp of the ore in an aqueous brine saturated with respect to the water-soluble ore components, dissolving 2,4-dichlorophenoxyacetic acid in the brine and then subjecting the pulp to froth flotation. I r

17. The process for benefication of an ore containing halite and sylvite which includes the steps of forming a pulp of the ore in an aqueous brine saturated with respect to the soluble ore components, dissolving in the brine a collector reagent yielding 2,4-diohlorophenoxyacetic ions in solution and subjecting the pulp to froth flotation.

ARTHUR. J. WEINIG] References Cited in the file ofthis patent UNITEDISTATES PATENTS Number Name Date 8 Number Name Date 2,280,451 Riddle Apr. 21, 1942 2,297,664 Tartaron Sept. 29, 1942 2,302,581 Schoeller Nov. 17, 1942 2,342,277 Herkenhoff Feb. 22, 1944 2,382,360 Weiner Aug. 14, 1945 2,453,983 Sexton Nov. 16,1948

OTHER REFERENCES Doremus, Proper Care of Brine Aids Prevention of Corrosion. Heating, Piping and Air Con- Div. 64.) j, 

1. IN A PROCESS FOR THE SEPARATION OF SYLVITE AND HALITE BY FROTH FLOTATION FROM A SATURATED PULP OF THE ORE, THE IMPROVEMENT WHICH COMPRISES ADDING TO THE PULP A BRINE SOLUBLE SALT OF 2,4-DICHLOROPHENOXYACETIC ACID. 